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Sewage is a water-carried waste, in solution or suspension, that is intended to be removed from a community. Also known as domestic or municipal wastewater, it is more than 99% water and is characterized by volume or rate of flow, physical condition, chemical and toxic constituents, and its bacteriologic status (which organisms it contains and in what quantities). It consists mostly of greywater (from sinks, tubs, showers, dishwashers, and clothes washers), blackwater (the water used to flush toilets, combined with the human waste that it flushes away); soaps and detergents; and toilet paper (less so in regions where bidets are widely used instead of paper). Whether it also contains surface runoff depends on the design of sewer system. All sewage ends up back in the environment (from which its constituents came), by any of several routes. A basic distinction in its route is whether it undergoes sewage treatment to mitigate its effect on the environment before arriving there. Sewage usually travels from a building's plumbing either into a sewer, which will carry it elsewhere, or into an onsite sewage facility (of which there are many kinds). Whether it is combined with surface runoff in the sewer depends on the sewer design (sanitary sewer or combined sewer). Before the 20th century, sewers usually discharged into a body of water such as a stream, river, lake, bay, or ocean. There was no treatment, so the breakdown of the human waste was left to the ecosystem. Today, the goal is that sewers route their contents to a wastewater treatment plant rather than directly to a body of water. In many countries, this is the norm; in many developing countries, it may be a yet-unrealized goal. In general, with passing decades and centuries, humanity seeks to be smarter about the route of sewage on its way back to the environment, in order to reduce environmental degradation and achieve sustainability. Thus other goals of modern sewage routing include handling surface runoff separately from sewage, handling greywater separately from toilet waste, and coping better with abnormal events (such as peaks in use from internal displacement and peaks in stormwater volumes from extreme weather). Proper collection and safe, nuisance-free disposal of the liquid wastes of a community are legally recognized as a necessity in an urbanized, industrialized society.〔McGraw-Hill Encyclopedia of Science and Technology (View excerpt at (Answers.com )〕 The reality is, however, that around 90% of wastewater produced globally remains untreated causing widespread water pollution, especially in low-income countries: A global estimate by UNDP and UN-Habitat is that 90% of all wastewater generated is released into the environment untreated. In many developing countries the bulk of domestic and industrial wastewater is discharged without any treatment or after primary treatment only. The term sewage is nowadays regarded as an older term and is being more and more replaced by "wastewater". In general American English usage, the terms "sewage" and "sewerage" mean the same thing.〔Funk & Wagnall's Standard Dictionary (International Edition) New York, 1960, p. 1152.〕〔 〕〔 〕 Both words are descended from Old French ''assewer'', derived from the Latin ''exaquare'', "to drain out (water)". In American technical and professional English usage, "sewerage" refers to the infrastructure that conveys sewage. ==Types== * The wastewater from residences and institutions, carrying body wastes (primarily feces and urine), washing water, food preparation wastes, laundry wastes, and other waste products of normal living, are classed as domestic or sanitary sewage. * Liquid-carried wastes from stores and service establishments serving the immediate community, termed commercial wastes, are included in the sanitary or domestic sewage category if their characteristics are similar to household flows. Wastes that result from an industrial processes such as the production or manufacture of goods are classed as industrial wastewater, not as sewage. * Surface runoff, also known as storm flow or overland flow, is that portion of precipitation that runs rapidly over the ground surface to a defined channel. Precipitation absorbs gases and particulates from the atmosphere, dissolves and leaches materials from vegetation and soil, suspends matter from the land, washes spills and debris from urban streets and highways, and carries all these pollutants as wastes in its flow to a collection point. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Sewage」の詳細全文を読む スポンサード リンク
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